4L60E: PR Valve (Part 3) Torque Signal Oil Pressure (4L60E Line Pressure) 

Right on. Appreciate your comment.

Glad you're getting something of value out of these videos. Really appreciate you taking the time to write what you wrote. Thank you.

The positive feedback is appreciated. Thank for dropping me a line! PS - If it feels right to you, please help me spread the word about this channel. 1 Handed Transmission Rebuilder: (60-Sec Preview) ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-y3Vixa_Ec1E.html

Always aiming to create something worth watching. Thanks for dropping me a line.

@@SouthpawAutoworks by

Glad you enjoyed it. Thanks for dropping me a line.

Right on!

Lot of work...but, it's a labor of love.

Better late than never... Welcome aboard!

Many thanks for the feedback. Thanks for dropping me a line, Marcelo.

You're welcome. Thanks for dropping me a line! PS - If it feels right to you, please help me spread the word about this channel. 1 Handed Transmission Rebuilder: (60-Sec Preview) ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-y3Vixa_Ec1E.html

Right on!

Yes, I remember you mentioning that, James. You had brought up a great point! Those oil schematics/diagrams are overwhelming to look at. I intend to dedicate a video to making sense of the oil diagram. Unfortunately, I don't feel comfortable "borrowing" a diagram off of the internet (or even out of a book), for copyright/intellectual property reasons. With that said, I'll have to create a diagram from scratch. There goes x hours. haha. It'll eventually get done. Everything in time... Dude, thanks, as always, for watching....and dropping me a line! Always good to hear from you, man! How's the sale of the '67 Firebird coming along?

Right on! Welcome aboard. The GM evolution of this trans (700R4 to 4L60E) is pretty cool. As you know, the VB is an electronic-over-hydraulic design. Gonna be making a video about how the shift solenoids, and their respective shift valves, work together...soon. The 4L60E is riddled with shortcomings (mechanically and hydraulically). However, with a little love, it can be a great transmission. Got a lot more 4L60E videos in the works. Recently released an AFL video. Here's a 60-second preview of it: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-yfXdx6AkqjU.html Thanks for dropping me a line!

Right on!! I really appreciate you taking the time to write what you wrote. Thanks for dropping me a line!

Were you ever able to get to the bottom of the issue?

You're welcome! Appreciate you dropping me a line.

Glad you got something out of it. Thanks for dropping me a line.

Same to you!

Such a bummer... However, I gotta give you kiddos for your perseverance. As you already know (from the video), that pressure is too low. As time permits, I'm gonna look over some notes, think about this one some more, and get back to you...probably with some questions. The positive feedback about the videos is appreciated. Thanks for dropping me a line! PS - If it feels right to you, please help me spread the word about this channel. 1 Handed Transmission Rebuilder: (60-Sec Preview) ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-y3Vixa_Ec1E.html How the 4L60E valve-body works: (60-Second Preview) ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-fWPSaLeaOXI.html

Clean the epc solenoid screen from dirty nothing more you get 170psi 😝

Happy New Year, man!

Dude, thanks for watching! Appreciate you.

That's a bit odd. People typically complain about the 1-2 up-shift being too firm....not too soft. There's a number of things that control shift feel. When time permits, I'll dedicate a video to this topic.

You bet.

If it were me, I'd be: 1). Looking at Converter Clutch Valve, in pump (can easily be installed backwards). 2). Looking at TCC lock-up valve in VB (Regulator Apply Valve & Isolator Valve). 3). Verifying cooler flow. 4). Etc. Would love to hear what you find.

Great question! Yes, a stronger spring can be installed. Per this video series, 1). The large outer spring is responsible for determining the base line pressure (Stock is roughly 55 psi). 2). For pressures to be elevated above 55 psi, the boost valve must assist the large outer spring. There are a number of ways to increase line pressure above the stock pressure values. We will be covering that in future videos. Stay tuned!

Your positive feedback is appreciated. It sounds like your 4L60E is slipping during one of the up-shifts? Is this correct? Questions: With the shifter in "P", start the engine, and shift to "D." And drive the vehicle. 1). When the trans shifts from 1st gear to 2nd gear, what happens? 2). When the trans shifts from 2nd gear to 3rd gear, what happens? 3). When the trans shifts from 3rd gear to 4th gear, what happens?

I can't be giving away all of my secrets... ;)

You may be dealing with a bad AFL Valve. If you haven't done so already, check out the videos listed below. I have not created the 3-4 shift valve video, yet....just a matter of time. However, the 1-2 shift valve and the 3-4 shift valve are similar in function. I'm happy to elaborate on the AFL Valve...but, everything will make more sense after watching the videos below. 4L60E: AFL Valve: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-LqBkdegPjNk.html 4L60E Shift Solenoid: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-FaChWmcsAgI.html 4L60E: 1-2 Shift Valve: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-jPhm76RDz6Y.html

Regarding the engine braking... Regarding engine braking, or lack of it with trans in 3rd gear, and shifter in D (as opposed to 3). Under those conditions, it's normal to not have engine braking. There's a one-way clutch (Input Sprag) that intentionally creates coasting when you let off the throttle. However, when the trans is shifted into 3, there's an extra clutch pack (Overrun) that's activated, that essentially locks up the one-way clutch, and creates engine braking.

@@SouthpawAutoworks I watched all the videos. Supper great and easy to understand. I also watched: 4L60E: PR Valve (Part 3) Torque Signal Oil Pressure (4L60E Line Pressure). This one leads a much better understanding of why, when I open the throttle to increase load, the trans shifts back into 4th gear. With that in mind it seems that line pressure must be dropping as the oil heats up? maybe a weak spring in the AFL and the AFL line pressure is just low? Maybe the signal pressure to the PR Boost valve is low when heat is up and RPM's are lower and at light throttle? Maybe a bad EPC resulting in a lower torque signal pressure? What am I not seeing? Is there an electronic pressure sensor somewhere that the computer uses to control the EPC?

Mark, Thank you for taking the time to check out each of the videos. I'm thinking you could be dealing with a worn out AFL Valve. This is gonna be a long one to read... Long Story Short: A worn out AFL Valve can result in low Signal Oil pressure at the reaction end of the 3-4 Shift Valve. Lower than normal oil pressures, at this end of the valve, can make it impossible to overcome the spring "pressure" at the other end of the valve...sometimes (depends on engine load). This can result in a "falls out of 4th gear" condition. Note: I say spring "pressure", because it's technically spring tension...not pressure. However, I am attempting to keep things apples-to-apples (oil pressure vs spring pressure), for the sake of simplicity. If you want a more detailed explanation, continue reading... Line Pressure: 55 - 300+ psi. Line pressure is fed to the AFL Valve, where it's regulated/modified: 55 -115 psi. That AFL Fluid is sent to the 1-2 Orifice in the Separator Plate, where it becomes Signal Oil. That Signal Oil is sent right between the reaction end of the 1-2 Shift Valve and the snout of the 1-2 Shift Solenoid. I have yet to get to the 2-3 or 3-4 Shift Valve videos...but, the 3-4 Shift Valve operates just like the 1-2 Shift Valve (oil pressure at one end, and spring "pressure" at the other end). In fact, when the 1-2 Shift Valve moves, the 3-4 Shift Valve moves, at the exact same time (at least in 1st gear). So, when the 1-2 Shift Solenoid is energized, this action prevents the 1-2 Signal Oil from escaping, back to the oil pan. This builds oil pressure. This pressure pushes on the reaction end of the 1-2 Shift Valve. It creates enough oil pressure to overcome the spring "pressure" at the opposite end of the valve. Then the valve moves in the direction of the spring. The 1-2 Shift Valve and the 3-4 Shift Valve share the same Signal Oil. So, when we build oil pressure at the reaction end of the 1-2 Shift Valve, we're also simultaneously building oil pressure at the reaction end of the 3-4 Shift Valve. 3-4 Up-Shift: The PCM commands the 1-2 Shift Solenoid ON. This traps 1-2 Signal Oil, and builds pressure at the reaction end of the 3-4 Shift Valve. This oil pressure becomes greater than the spring "pressure" at the opposite end of the valve. The 3-4 Shift valve moves in the direction of the spring. Bringing it Full Circle: When the AFL Valve wears out, it becomes most noticeable during low load conditions (light throttle/cruising). Line Pressure varies greatly. But we know, during low load conditions, that Line Pressure can be as low as roughly 55 psi. This is normal. We also understand that the AFL Fluid can operate as low as 55 psi. Also normal. When the AFL Valve is worn out, it's possible for the AFL Fluid to drop below 55 psi. And that's where problems can start occurring. - I've been told, by folks that have tested these things, that when AFL Fluid pressure drops as low as 48 psi, that the 3-4 Valve will not move towards the spring. There's simply not enough oil pressure to overcome the spring "pressure." 48 psi VS 3-4 Shift Valve: When the AFL Fluid pressure drops to 48 psi, this means that the 1-2 Signal Oil pressure drops to 48 psi, too. Unfortunately, 48 psi is not enough oil pressure to overcome the spring "pressure". How does it make the 3-4 up-shift, but not stay in 4th gear? Under heavier throttle conditions (like acceleration), Line Pressure is higher...therefore, AFL & Signal Oil pressures are higher...higher than 55 psi. However, after the vehicle get's up to speed, we naturally lift off of the throttle, quite a bit, and just cruise. As we cruise, the Line Pressure is lowered...and everything else drops with it. - So, under moderate acceleration, there will be enough Signal Oil pressure to move the 3-4 Shift Valve (resulting in a 3-4 up-shift). However, as we let off of the throttle, and the oil pressure drops below 55 psi (because of our worn out AFL Valve), and we now do not have enough oil pressure to overcome the spring "pressure"....and the valve is pushed away from the spring, resulting in a un-commanded/un-intentional 4-3 down-shift. Temperature: As the ATF (automatic transmission fluid) warms up, it becomes thinner. Also, metal parts expand and contract with temp changes. Point being, a leaky circuit will leak even more as the temps increase. Valve vs Bore: I say a worn out valve. Typically, it's actually the valve bore that wears out. One way to fix the problem is to ream out (oversize the bore), and install an over-sized AFL Valve. Parts and Tools: Here's one way to go about fixing the bore... Reamer Kit: ebay.us/XMR3Ux AFL Valve Solution: ebay.us/R3GPnF DISCLOSURE: 🕵 Links provided are affiliated links with the associated websites. While there is no extra cost to the purchaser, a small portion of the sale goes to support this RU-vid channel.

Great question. It will affect Torque Signal oil pressure, which ultimately affects line pressure. It's a way to raise the line pressure. This can have positive effects. However, it can also have negative effects, too. I plan on making a video on this topic, when time permits. Currently assembling a 4L60E, in prep for a bunch of 4L60E videos. Stay tuned!

When the shifter (inside the vehicle) is moved, ultimately it moves the Manual Valve, which is located inside the valve-body. Anytime the engine is running, the pump moves fluid through various sections of the transmission. However, when the trans is shifted into Neutral, the Manual Valve stops the oil from flowing to the clutch packs......resulting in no gears (neutral). The Manual Valve has a number of jobs. In other words, it does more than just create Neutral. Hope this makes sense.

Thanks a lot!

You bet!

Unfortunately, I don't do email for comments. It would be one more thing to monitor... You could upload a pic to your YT profile. Click on the "CREATE" button, in the upper right-hand corner of the screen. Select "Create post." You'll have an option to add an image. There may be size requirements... If all else fails, you could upload a short cell phone video, to your profile. Let me know when you have a video/image uploaded, and I can visit your channel, and take a look.

Hello there!

@@SouthpawAutoworks video posted still too few,I can only get a glimpse of how valve body works ,there r lots video detail how engine works

Great question. Unfortunately, it's not as simple as unplugging the TCC PWM Solenoid. However, the solution is pretty simple and inexpensive (in my opinion). This VB kit (listed below) includes a valve-train that converts PWM TCC apply, and makes it an On-Off apply. amzn.to/3jjJp9o (paid link) That's correct. 93-94 are On-Off TCC apply (no PWM TCC solenoid). 95-Up have the PWM TCC Solenoid. DISCLOSURE: 🕵 As an Amazon Associate I earn from qualifying purchases. Some, if not all, of the links contained in this video description (comment thread) are affiliate links. This means that, at no additional cost to you, I will receive a small commission on any purchases you make through the website links provided above.

I'm having trouble understanding your question. Can you rephrase the question?

Thank you for taking the time to provide detailed information with your question. I'd like to attempt to assist you. However, in order for that to happen, I will need more information. Getting everyone on the same page is important. However, that can be a real challenge to do that via RU-vid comments. I'm currently working on a video series that will enable me and viewers, like yourself, to communicate with greater ease, about 4L60E transmission problems. I'm adding your name to a list. When I get those videos completed, I will notify you. Thanks for your patience. Thank you for dropping me a line.

@@SouthpawAutoworks ok thank you and plz make it asap 😜

Without looking at the vehicle (and getting more info), I can't say... Here's some general info: As the trans heats up, the metal & fluid heat up, too. If there's a crack in an aluminum piston, the crack will grow larger as the piston heats up (expanding metal). As the fluid heats up, it gets thinner. If the trans is dealing with an internal leak, the leak will get worse as the fluid gets thinner.

Congrats on your first rebuild! That's really exciting. Sorry to hear about your setback. This kinda stuff happens... Questions: 1). Are you certain that you had the fluid level set correctly? 2). With the shifter in OD mode, what gear(s) was it slipping in? 3). Would it slip only when the engine/trans was cold? Only slip when hot? Or it slipped all the time, regardless of engine/trans temp? 4). If you shifted the trans to D1, D2, D3, would the slipping problem go away? 5). Did it slip in Reverse? 6). Were you previously able to attach a transmission pressure gauge (capable of reading oil pressures over 300 psi), and get a pressure reading, at idle, and while driving? 7). Do you currently have a check engine light on? Do you have any codes for the trans and/or engine? 8). What was your original transmission failure? (3-4 clutch failure, 2-4 band failure, etc) 9). What was the original symptom? (slipping in one gear, or multiple gears? Erratic shifting? Or something else?) I've got other questions, regarding your rebuild. But, let's start here...

@@SouthpawAutoworks Thanks, but right now I am wishing I would never attempted it. I have spent a lot of money on good parts and I am stuck with this thing not working hardly at all. 1) I did check the fluid with the engine running and everything up to temp. Fluid was just above second hole on the dip stick. 2) With the shifter in drive it is very slow to go into gear. Same with reverse. It was slipping in every gear but now it won’t even shift to second. When stopping and taking off again there is a delay before it reacts and then it goes but if you let off and stab the gas it slips and grabs but like I said it won’t even go in to second now. 3)It slipped while at about 100 degrees and kept slipping even at 160-180. 4) The slipping happens no matter where the gear selector is. 5) It slips in reverse a little bit also there is quite delay for it to engage as well. It acts much like it does in first. 6)I am not quipped to check line pressure. 7) There are no codes for trans. or engine. 8)Original failure was 3-4 clutch failure. Last builder did many things that would cause this to happen prematurely. One of the things was eliminating the check ball capsule that is located near the second gear servo bore. Also left out the reaction springs in the input drum. 9) The original symptom was slipping in 4 gear while at highway speeds. If you tried to accelerate even a little the engine rpm would climb but no acceleration. The problem progressively got worse and eventually when I finally decided it needed rebuilt it was slipping in every gear. I used a Raybestos rebuild kit and in addition did a Raybestos Z-Pack for the 3-4 clutch. I also used a Sonnax Smart shell and 5 pinion planets. I would say 80 percent of the internals are new. I did not skimp and I was so careful to check spacing tolerances and make sure everything was just right. No corner cutting. I am beyond aggravated… I must have done something wrong 😑

If it's slipping in all gears, and in all gear modes (OD, D1, etc), it makes me lean towards a Line Pressure issue. It would be best to verify, so you're not chasing your tail. If it were me, I'd be putting it back together, filling it up with oil, and checking Line Pressure with the engine idling. Note: I know that you mentioned that you are not currently equipped to check line pressure. You previously asked about the EPC Solenoid (aka Force Motor). If there's a problem with the EPC Solenoid, yes, it can cause line pressure issues. But, it's one of many things that affect line pressure. Line Pressure is influenced by: 1). Variable pump output (pump slide). 2). Pressure Regulator Valve. 3). PR Valve bore in pump (the bore can wear out). 4). Boost Valve & Sleeve. 5). EPC Solenoid. 6). AFL Valve (bore can wear out). 7). PCM (controls EPC Solenoid). 8). Various engine sensors (MAF, TPS, etc)(PCM monitors these and makes "decisions" that affect the Line Pressure (via the EPC Solenoid). Questions: 1). Year/make/model? 2). Did you replace all of the electrical? (Solenoids, harness, pressure switch, speed sensors, etc) 3). Did you happen to replace the VB (valve-body) separator plate?

@@SouthpawAutoworks Ok I had to walk away from it for a few days for my own sanity. LOL I went and got a pressure testing setup and I am glad I did. After it warmed up it is only at 20psi. It is the same wether it is in P, D, or R. I also rigged up a way to drive with it connected and I think that was even more telling. It will not shift out of first at all, but in first when you accelerate the pressure goes up to about 100psi and then immediately dips down below 30 and is kind of erratic from there. This was done with the gauge connected to the port on the drivers side of the transmission where I usually have my temp transducer, so right off the pump I would presume. 1) 1999 GMC Sierra originally had a 4.8L engine. Trans is a 4L60e 2) I did replace the electrical just to be safe but the old solenoids and harness seemed to be fine. I had no issues like what I am having now. I did put the old Force motor back in just to test and it did not make a difference at all. 3)The separator plate is an aftermarket Transgo that had been put in there on the last build. That build only lasted about 50k miles. It was in perfect condition, i.e. no damage from the check balls slamming into the plate. I am thinking I have a problem in the pump.. What do you think? I really appreciate your time helping me out with this and the time and effort you put in to your videos and animations. It really cool to get to understand the inner workings of these things.

Totally understand. ha It's good to take a break, as these kind of setbacks can, and will, get pretty damn frustrating. Thank you for answering each of my questions. I appreciate your attention to detail. I'm really glad to hear that you were able to get your hands on a pressure gauge. It's a super useful tool. There's only one (1) pressure port on the 4L60E (Line Pressure). So, you're good there. The problem definitely could be in the pump. But, it's important to remember that the pump moves oil....however, it does not create oil pressure. As the oil exits the pump, the oil travels to various valves, accumulators, through small holes in the separator plate, to the clutches, etc. As the oil goes through small holes, the oil slows down. As the oil encounters dead ends in a circuit (clutch packs, servos, etc), the oil stops flowing in that direction. It's this resistance (and dead-ends) that creates oil pressure. So, what I'm saying is...it's possible that the pump is doing its job (moving oil). However, there could be a large leak somewhere down-stream of the pump. There are some hydraulic circuits that are active in all shifter positions (Park, Reverse, Neutral, etc). Questions: 1). You mentioned 20 psi with the trans warmed up. What's the pressure when the trans/engine is cold? (with the trans in Park, engine idling). 2). If you unplug the wiring harness from the trans, the line pressure will increase to max values...or at least it should. Note: Unplug the harness with the engine off. With the wiring harness disconnected, what is the line pressure with the trans in Park, and the engine idling... A). What is the pressure with the engine/trans cold? B). What is the pressure with the engine/trans warmed up? I've got other questions regarding your rebuild, but I'm out of time today.

You're so right. They are very similar. Would love to do that...when time permits. Thanks for dropping me a line!

@@SouthpawAutoworksyour welcome

What year is the Escalade? Sounds like 1st, 2nd, and 3rd gear work......is this correct? When the trans is in 3rd gear, and it should up-shift to 4th, what happens? It simply stays in 3rd gear? (Like it's stuck in 3rd gear) It tries to up-shift to 4th gear, but the engine revs up, and the vehicle starts to lose forward momentum?

@@SouthpawAutoworks yes exactly what you're saying.. what do you think is the issue?

@@SouthpawAutoworks 2003 cadllac escalade 6.0 L engine

@@SouthpawAutoworks No problem shifting from 1st to 3rd gear then it stays in thiird and just revs up doesnt shifts anymore.but it stills goes forward just stuck in 50-60kmp when tries to step on gas just revs up

Great question. The EPC Solenoid is N.O. (Normally Open). In other words, when no electrical power is being supplied to the 4L60E, the EPC Solenoid's internal valve will be open. AFL fluid enters the screen that located the furthest from the the electrical connector. The AFL fluid exits through the other screen. However, when it exits through that screen, it becomes known as Torque Signal fluid (oil pressure).

@@SouthpawAutoworks if too much dirty on the input epc screen ill have low pressure or high pressure on the pressure line ?

@@SouthpawAutoworks ok ppz if you can check any 4l60e epc solonoid its closed when you give 12v open and when you cut the voltage closed you can test by oil on the valve body or clean it and by air from mouth 🤣🤣

If the EPC Solenoid screen (located on the separator plate) is really dirty, it'll starve the EPC Solenoid of incoming oil pressure. This means less oil pressure will make it to the Boost Valve...resulting in low line pressure. The base line pressure is right around 55 psi. As more load is placed on the 4L60E, line pressure must increase...this protects the clutches, and band, from slipping (burning up). The Boost Valve is responsible for raising line pressure, as need be. But the Boost Valve can't do its job properly if there are problems "upstream."

@@SouthpawAutoworkssorry you are wrong i test verry well the epc solenoid its NC not NO it mean when no power its closed not open

Great question. There's a number of reasons; 1). Driver comfort. When line pressure is maxed out, the transmission shifts harshly. Park to Reverse...bang. Park to Drive...bang. 2). Longevity of driveline. All of the harsh shifts are hard on U-joints, differentials, etc. 3). Fuel mileage. When line pressure is maxed out, the pump has to work harder to push more oil into the trans. The pump is driven by the engine....resulting in more parasitic losses (drag). Note: This can also wear the pump out faster. 4). Etc. Once again, great question.

Sorry to hear that. What problem are you experiencing?

The check-balls are 1/4" of an inch (0.250"). Thank you for supporting this channel. One-Armed Automatic Transmission Builder. (60-Seconds) ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-y3Vixa_Ec1E.html

Are you shure , seven are 0.250” , but one is bigger i remember